1. Field of the Invention
The present invention relates to engine automatic start stop control apparatuses that automatically stop engine idling in accordance with prescribed conditions.
This application is based on Patent Application No. Hei 11-224693 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
Recently, much attention has been directed to environmental problems such as increasing temperature on the earth. So, automobile manufacturers and institutes are actively developing electric vehicles and hybrid vehicles to reduce discharges of gases and matters such as carbon dioxide. The electric vehicles are optimal solutions to the environmental problems because of zero discharge of gas. Under the present situation, however, the electric vehicles must be further developed to cope with technological disadvantages, as follows:
(i) The present electric vehicles are capable of running only short distances with one-time electric charging.
(ii) The electric vehicles do not sufficiently measure up with capabilities and practical performance of the conventional vehicles using internal-combustion engines.
The hybrid vehicles are equipped with engines and motors, wherein batteries are charged in response to the speed of the engines. In prescribed low ranges of engine speeds where the engines produce relatively large amounts of carbon-dioxide discharges, the hybrid vehicles solely activate the motors or they activate both of the engines and motors in parallel, so it is possible to reduce amounts of carbon-dioxide discharges. The hybrid vehicles are practical solutions to the environmental problems because they are capable of reducing the carbon-dioxide discharges while securing performance (e.g., running distance and drivability) of the conventional vehicles. So, automobile manufacturers produce a variety of hybrid vehicles of practical use that are capable of running long distances by themselves.
Under the aforementioned circumstances, engineers pay considerable attention to engine automatic stop techniques, which automatically stop engines without driver""s instructions or operations and which are proposed for reduction of discharge gas and fuel consumption due to fuel combustion by automatically stopping engines idling. When the vehicles stop engine idling, the engines do not produce high-temperature discharge gases due to fuel combustion. However, when the engines do not discharge gasses, catalysts experience a decrease in operating temperature. Normally, the catalysts cause chemical reactions of discharge gases under prescribed temperatures, so that they reduce amounts of discharge gasses or matters such as nitrogen oxide (NOx). To realize reduction of discharge gasses due to fuel combustion, stopping, the engine idling brings temperature reduction of the catalysts. As a result, there occurs a problem in that when the engines are once stopped and then re-started,.discharge gasses are increased unintentionally.
It is an object of the invention to provide an engine automatic start stop control apparatus that is capable of reducing discharge gas by preventing a catalyst from experiencing a reduction in operating temperature when engine idling is stopped and restarted.
The present invention provides an engine automatic start stop control apparatus that controls an engine to be automatically stopped or started in response to driving conditions of a vehicle. Namely, the apparatus installs an outside air temperature detecting device (18, S100-S114) for detecting an outside air temperature of the vehicle, an engine water temperature detecting device (18, S200) for detecting an engine water temperature of the engine, and a determination device (18, SA20, SA22, SC18, SC20, S106-S114) for making a determination whether or not to allow stoppage of the engine on the basis of a relationship between the outside air temperature and the engine water temperature.
The determination device makes the determination whether or not to allow stoppage of the engine in consideration of the relationship between the outside air temperature and the engine water temperature. Hence, it is possible to maintain performance of a catalyst by avoiding its temperature reduction. As a result, it is possible to reduce discharge gas by securing normal operation of the catalyst.
In addition, an intake air temperature detecting device for detecting intake air temperature is installed inside of an intake air passage of the engine. So, the outside air temperature detecting device estimates the outside air temperature based on the intake air temperature which is detected by the intake air temperature detecting device after the vehicle runs for a prescribed amount of time.
Because the outside air temperature is estimated from the intake air temperature of the engine, it is unnecessary to provide a sensor exclusively used for measuring the outside air temperature.
The determination device allows stoppage of the engine if the outside air temperature fails within a prescribed temperature range and the engine water temperature is equal to or above a preset temperature.
If the outside air temperature falls within the prescribed temperature range, this invention inhibits idle stop of the engine under the condition where the engine water temperature is equal to or above the preset temperature. Hence, it is possible to prevent the catalyst from being rapidly deteriorated in performance due to rapid temperature reduction of the catalyst when the outside air temperature is low. Thus, it is possible to effectively reduce discharge gas even in a cold district.
The vehicle is equipped with an air conditioning control device (21) for controlling air conditioning of an interior space thereof. The determination device monitors operating conditions of the air conditioning control device. So, the prescribed temperature range of the outside air temperature and the preset temperature of the engine water temperature are changed in response to the operating conditions of the air conditioning control device.
In response to the operating conditions of the air conditioning control device, its setting temperature is changed to act as a threshold for allowing stoppage of the engine. Thus, it is possible to provide the driver with good driving conditions without damaging comfortableness in the interior space of the vehicle.